How long exposure to sun for vitamin d

This article explains exactly how much vitamin D you should be taking. This is a detailed review of vitamin D toxicity and how much vitamin D is considered too much.

Toxicity is rare, but can occur with extremely high…. Vitamin D is very important for your health, but it is possible to get too much of it. This article explores 6 side effects of taking too much vitamin…. Taking care of your skin should be an essential part of your health regimen. Learn about vitamins D, C, E,. There are several health benefits of sunlight. Adding a little sunshine to…. Vitamin D has numerous health benefits, but it's tricky to know which supplement to choose.

Here are 13 of the best vitamin D supplements, according…. Health Conditions Discover Plan Connect. However, too much sunlight comes with its own health risks. This article explains how to safely get vitamin D from sunlight.

Supplements Vitamin D. Expose Your Skin Around Midday. Does Sunscreen Affect Vitamin D? Dangers of Too Much Sunlight. The Bottom Line. Read this next. The Surprising Truth. The form of vitamin D that you get from the sun is called D3 also known as cholecalciferol , which is derived from cholesterol. The amount of vitamin D you get from exposing your bare skin to sun is dependent on several factors. They are:. For instance, if you live at a northern latitude like Anchorage, Alaska, your body would create less vitamin D during the winter than someone who lives in Miami, because Florida has more exposure to UVB rays that are necessary to produce vitamin D.

If you wear clothing that covers most of your skin, you may be at risk for vitamin D deficiency. Cloudy weather can also be a problem because fewer UVB rays reach your skin on cloudy days. People who have darker skin may also have trouble synthesizing vitamin D from the sun.

Essentially, this means that people who have pale skin produce vitamin D more quickly than people with darker skin. Skin-color typology is generally arranged into the following categories:. A good rule of thumb is to get half the sun exposure it takes for your skin to turn pink to get your recommended amount of vitamin D.

After you have exposed your skin for enough time, cover up with clothing and go back into the shade. A dark-skinned person might need 10 times more sun exposure than a lighter-skinned person to produce the same amount of vitamin D.

This occurs during the early and later parts of the day, and most of the day during the winter. The rigid planar structure of 7-dehydrocholesterol sandwiched in between the triglyceride fatty acid hydrocarbon tails could only be transformed into the planar czc conformer of previtamin D 3 upon exposure to solar UVB radiation Fig.

Proposed theoretical structural model for the localization of the cZc-previtamin D 3 in the phospholipids of a membrane. Based on the amphipathic nature and conformational mobility of previtamin D 3 , we proposed the following model to show the spatial relationship between previtamin D 3 and phospholipids.

A, phosphatidylcholine; B, cZc-previtamin D 3. Once formed, this unstable conformer rapidly converted to vitamin D 3. Effects of phospholipid carbon chain length and saturation on the rate of pre-D 3 to vitamin D 3 isomerization in liposomes. Because vitamin D 3 is thermodynamically more stable and also more flexible it is ejected out of the plasma membrane into the extracellular space and diffuses into the capillary bed in the dermis where it is bound to the vitamin D binding protein DBP for transport to the liver.

There has been a lot of discussion as to whether ingesting vitamin D from the diet or from a supplement is the same as producing vitamin D 3 in the skin. A schematic representation of the photochemical and thermal events that result in the synthesis of vitamin D 3 in the skin, and the photodegradation of previtamin D 3 and vitamin D 3 to biologically inert photoproducts. Vitamin D 3 exits the skin into the dermal capillary blood system and is bound to a specific vitamin D-binding protein DBP.

When previtamin D 3 and vitamin D 3 are exposed to solar UV B radiation, they are converted to a variety of photoproducts that have little or no activity on calcium metabolism.

During exposure to sunlight after previtamin D 3 is produced it will absorb solar UVB radiation and isomerize into two major photoproducts, lumisterol 3 and tachysterol 3 Fig.

Neither of these two photoproducts has any effect on calcium metabolism. In addition when vitamin D 3 is made from previtamin D 3 in the skin if it is exposed to solar UVB radiation it will absorb UVB radiation and be converted into several suprasterols and 5,6-trans-vitamin D 3 Figs. In addition previtamin D 3 can also be converted to several toxisterols Fig. An analysis of the photolysis of 7-dehydrocholesterol 7-DHC in the basal-cell layer and the appearance of the photoproducts previtamin D 3 Pre-D 3 , lumisterol 3 L , and tachysterol 3 T with increasing time of exposure to equatorial simulated solar UV radiation.

Bars above data points show the standard error of the mean of three determinations. When vitamin D 3 is irradiated, it is converted to 5,6-trans-vitamin D 3 and at least 6 photoproducts known as suprasterols. Once previtamin D 3 is formed, it has the ability to rotate around the 6—7 bond. Relaxation via rotation about the 6—7 bond followed by UV irradiation can give rise to a wide variety of toxisterols and tachysterol.

This however does not mean that these myriad of photoproducts don't have other biologic effects such as regulating epidermal cell growth and reducing risk of skin cancer. One product, lumisterol 3, if converted to 1,dihydroxylumisterol 3 may have anti-tumor effects in the skin. Therefore sensible sun exposure to produce previtamin D 3 , vitamin D 3 and its photoproducts may have some additional benefits above and beyond simply taking a vitamin D 3 supplement or ingesting vitamin D 3 from dietary sources.

Suprasterols 5 and 6 show a strong antiproliferative activity as well as the positive control 1,25 OH 2 D 3. B Dose dependent antiproliferative activity of suprasterols 5 and 6 compared with 1,25 OH 2 D 3 in keratinocytes.

Therefore increasing the path length by which solar UVB has to travel through the ozone layer will result in a decrease in the number of UVB photons that reach the earth's surface Fig.

People who live farther North and South often cannot make any vitamin D 3 in their skin for up to 6 mo of the year. This angle is increased at higher latitudes, early morning and late afternoon when the sun is not directly overhead, and during the winter months. Therefore, at higher latitudes, greater distance from the equator, more of the UVB radiation is absorbed by the ozone layer thereby reducing or eliminating the cutaneous production of vitamin D 3. Influence of season, time of day, and latitude on the synthesis of previtamin D 3 in Northern A and C and southern hemispheres B and D.

The hour indicated in C and D is the end of the 1 h exposure time. Values are percentages of initial 7-DHC. Reproduced with permission from Ladizesky. People who live in the far Northern and Southern hemispheres had apparently appreciated this fact and were able to satisfy their vitamin D requirement by eating vitamin D rich foods including oily fish, seal blubber, polar bear liver and whale blubber and liver all of which contain large amounts of vitamin D 3.

In the early morning and late afternoon the zenith angle of the sun is also more oblique similar to winter sunlight and as a result very little if any vitamin D 3 can be produced in the skin before 10 a. The measurements were conducted after exposing ampoules filled with 7-DHC to sunlight. Holick, copyright , reproduced with permission.

Air pollution including nitrous oxide and ozone is common in many large cities including Los Angeles and San Diego Fig. The amount of sulfur dioxide ppm measured over a one hour period in San Diego, Los Angeles, San Francisco, and Sacramento on the same day.

B Absorption spectrum of ozone which also absorbs UVB radiation. An analysis of sun-induced vitamin D 3 synthesis in vitro was conducted at higher altitudes at the same latitude during the same month. In November in Agra very little previtamin D 3 was produced during exposure to the sun. It was observed that there was a direct correlation with increased previtamin D 3 production with increased altitude.

At Mt Everest base camp min there was almost a 5-fold increase in previtamin D 3 production compared with what was observed in Agra Fig. Ampoules containing 7-dehydrocholesterol in ethanol were exposed for 1 h between a. The conversion of 7-dehydrocholesterol to previtamin D 3 and its photoproducts was determined by HPLC. Sunscreens were designed to absorb solar UVB radiation.

Therefore the topical application of a sunscreen with an SPF of 30 reduces the capacity of the skin to produce vitamin D 3 by the same amount i. To convert nanograms of vitamin D per mL to nanomoles per L, multiply by 2. Serum concentration of hydroxyvitamin D in longterm sunscreen users and in age- and sex-matched controls from same geographical area.

Blood samples were obtained simultaneously from patients and controls. Humans evolved at the equator. They were constantly exposed to sunlight and developed an efficient natural sunscreen melanin, 49 which has an absorption spectrum of — nm and thus can effectively absorb solar UVB radiation Fig.

This was demonstrated when adult whites skin type 2 and blacks skin type 5 were exposed to the same amount of UVB radiation in a tanning bed. Whereas the white adults raised their blood levels of vitamin D 3 more than 30 fold the black adults demonstrated no significant increase in their blood levels of vitamin D 3. However when the black adults were exposed to 5 times more UVB radiation, they increased their blood level by about fold Fig.

Absorption spectrum of melanin. In two lightly pigmented Caucasian A and three heavily pigmented Afroamerican subjects B after total body exposure to 0. Heaney, copyright Surface is a hyperboloid, plotting equation and was fitted to data by least squares regression methods. Skin pigmentation or the lack thereof was important in the evolution of humans as they migrated North and South of the equator.

Africans such as the Maasai Fig. Although there have been several explanations for why skin pigment devolved as humans migrated North and South of the equator one of the most likely explanations is as humans migrated farther North and South of the equator the zenith angle of the sun increased resulting in a decrease in the amount of solar UVB radiation reaching the earth thereby reducing vitamin D 3 synthesis. A decrease in the amount of skin pigment resulted in a decrease in the sun screening protection permitting more of the UVB radiation to reach the epidermal cells.

This provided an evolutionary advantage by being more efficient in producing vitamin D 3. This however did not make a lot of sense since heavy pigmentation and excessive hair would markedly reduce cutaneous production of vitamin D 3 which was essential for maximizing skeletal health throughout life thereby reducing risk of life-threatening fractures. However, more important is the fact that vitamin D deficiency in utero and during the first few years of life would have caused infantile rickets resulting in a flat deformed pelvis with a small pelvic outlet.

Furthermore vitamin D is important for muscle function which is also crucial for birthing. Therefore in order to survive and procreate skin pigmentation had to markedly decrease in order to permit more UVB photons to enter the skin to produce sufficient amounts of previtamin D 3.

It was observed that 7-dehydrocholesterol concentrations in human epidermis were inversely related to age Fig. The increase in the blood level of vitamin D 3 in six young adults aged 20—30 was at least three-fold higher compared with the six older adults aged 62—80 demonstrating that aging significantly decreased the capacity of the skin to produce vitamin D 3 Fig. The skin has a large capacity to produce vitamin D 3. Exposure of a young adult in a bathing suit to one minimal erythemal dose MED of UV radiation in a tanning bed was equivalent to ingesting approximately 20, IUs of vitamin D 2 Fig.

The percent increase in circulating 25 OH D concentrations was similar to what was observed in healthy young adults Fig. Ampoules containing 7-DHC that were also irradiated served to demonstrate the efficacy of the tanning bed in producing previtamin D 3 Fig. A linear regression analysis revealed slopes of Circulating concentrations of vitamin D in healthy young and elderly volunteers exposed to UV radiation.

Comparison of serum vitamin D 3 levels after a whole-body exposure in a bathing suit; bikini for women to 1 MED minimal erythemal dose of simulated sunlight compared with a single oral dose of either 10, or 25, IU of vitamin D 2.

Production of previtamin D 3 and serum level of 25 OH D after the exposure of 7-DHC solution in ampoules and human volunteers to a tanning bed lamp. A Ampoules containing 7-DHC were placed and exposed to a tanning bed lamp. B Healthy young adults were exposed to 0. Circulating concentrations of 25 OH D were determined at baseline and once a week thereafter. C A healthy y-old man was exposed to tanning bed radiation equivalent to 0.

His circulating concentrations of 25 OH D were obtained at weekly intervals. Holick copyright , reproduced with permission from. The UVB lamps and residents in a day room of a nursing home. This was also supported by the fact that hours of sun exposure was directly related to circulating concentrations of 25 OH D Fig. B Seasonal fluctuation of serum 25 OH D according to frequency of sun exposure. Mean circulating hydroxyvitamin D levels in children, adolescents, and adults according to geographic latitude.

However another study reported that those living at the highest latitudes in Europe at higher circulating concentrations of 25 OH D Fig. Relationship between the serum 25OHD concentration and northern latitude in Europe. The likely explanation is that some people living far North and South of the equator who could not make any significant amount of vitamin D 3 in their skin for more than half of the year Fig.

People have a feeling of wellbeing when exposed to sunlight. This led to the use of solariums as a way to treat patients with tuberculosis and gave rise to the use of heliotherapy to improve health. One of the first association studies relating sun exposure with reduced risk for cancer was reported in by Hoffman, 74 who found that living at a higher latitude was associated with an increased risk for mortality from cancer.

He compared cancer mortality between and and observed that cancer mortality increased with increasing distance from the equator Fig. Mortality from cancer in cities according to latitude, — Four years later, Apperly 76 compared total cancer mortality in the populations studied with the percentage of Americans and Canadians in the same population who were engaged in agriculture.

He concluded that cancer mortality was highest in farmers living in the Northeast compared with those living in the South Fig. He concluded that the fact that these Southern farmers had nonmelanoma skin cancer resulted in them developing an immunity to the skin cancer which also resulted in an immunity to all cancers including those with high mortality rate.

Showing the relation of total cancer mortality rates to Smith's Solar Radiation Index in the American states, white population only. These observations essentially went unnoticed and the curious relationship of increased sun exposure and living at a lower latitude reducing risk of cancer mortality was buried in the literature.

Forty years would pass before Garland et al. United States, — These results together suggested that living at higher latitudes meant less exposure to vitamin D producing sunlight and therefore the connection with the first association with latitude and cancer mortality could be linked to an inverse relationship with cancer mortality and vitamin D status.

A Latitude vs. B Latitude vs. A multitude of epidemiologic studies followed these initial observations not only in the United States and Canada but worldwide. Grant 79 reported a dramatic inverse relationship between premature mortality due to cancer with UV exposure in both men and women Fig. In the United States, inverse associations with exposure to solar UVB radiation and cancer risk and mortality were reported for ovarian 80 and breast cancer, 81 cancers of the digestive system 79 , 82 and prostate cancer.

Giovannucci et al. Luscombe et al. It was also reported that adults who developed lymphoma had a decreased risk for mortality if they had more sun exposure as a teenager.

Also women over 40 y who had the most sun exposure lost the benefit since their risk was no different than those who had the least sun exposure. B Premature mortality due to cancer, white females, vs. Relative risk of cancer incidence and mortality related to solar UV-B exposure, northern vs. Covariables included in the Cox proportional hazards model: age, height, smoking history, and intakes of total calories, alcohol, red meat, calcium, retinol, and total fruits and vegetables.

Kaplan-Meier plot showing association of UVR exposure and age at diagnosis with prostate cancer. The observational and epidemiologic studies relating increased latitude with increased risk for cancers suggest a possible role of sun induced vitamin D 3 synthesis as the beneficial factor responsible for these observations.

Effect of cholecalciferol on rate of rise of PSA. Median and quartiles of rate of PSA increase prior to starting cholecalciferol visits —4 to —2 and visits —2 to 0 and after starting cholecalciferol visits 0 onward. Lappe et al. The Women's Health Initiative WHI initially reported that women who took mg of calcium and IUs of vitamin D 3 daily for up to 8 y had no reduced risk for colorectal cancer. Kaplan-Meier survival curves i.

Copyright Robert P. Heaney, Cod liver oil was used in the mids to treat tuberculosis. Hope-Simpson had speculated that there was a seasonal stimulus responsible for reducing infectious diseases during the summer. It is known for example that influenza infection is most prevalent in the winter months at latitudes North and South of the equator but is sporadic throughout the year in children and adults who live near the equator Fig.

It has been hypothesized that the seasonal variation could be due to a seasonal variation in circulating levels of 25 OH D. The seasonal and latitudinal distribution of outbreaks of type A influenza in the world, —, summarized from the Weekly Epidemiological Record of the World Health Organization into major zones.

The diagrams show for each calendar month the percentage of each zone's total outbreaks. In both north and south temperate zones the epidemics are distributed around the local midwinter, whereas the tropical zones show a transition, each approximating toward the distribution of its own temperate zone.

Macrophages play an important role in fighting infectious diseases by ingesting and then destroying them. This is one of the mechanisms believed to be responsible for vitamin D reducing risk of infectious diseases.

Liu et al. This was substantiated by Adams et al. Once 1,25 OH 2 D completes the task of maintaining normal cellular proliferation and differentiation, it induces the hydroxyvitamin Dhydroxylase OHase.

Thus, the local production of 1,25 OH 2 D does not enter the circulation and has no influence on calcium metabolism. There are a variety of association studies demonstrating that being born or living near the equator reduces risk of several autoimmune diseases.

Prevalence of multiple sclerosis MS by latitude in the United States according to data from Noonan et al. The dashed line is a quadratic fit to the data from Noonan et al.

A plot of the incidence of type 1 diabetes vs. Children younger than 14 y during — in 51 regions worldwide demonstrated a 10—15 fold increase in risk for developing type 1 diabetes if they were born in far Northern and Southern latitudes Fig. Data points are shown by dots; names shown adjacent to the dots denote location, where space allows. Where space was limited, numerical codes below designate location. Numerical codes for areas: 2. Beja, Tunisia; 3. Gafsa, Tunisia; 4.

Kairoan, Tunisia; 5. Monastir, Tunisia; 7. Mauritius; 8. Wuhan, China; 9. Sichuan, China; Huhehot, China; Nanjing, China; Jinan, China; Harbin, China; Changsha, China; Hainan, China; Hong Kong, China; Israel; Chiba, Japan; Hokkaido, Japan; Okinawa, Japan; Novosibirsk, Russia; Antwerp, Belgium; Varna, Bulgaria; Denmark; France; Baden, Germany; Attica, Greece; Sicily, Italy; Pavia, Italy; Marche, Italy; Lazio, Italy; Krakow, Poland; Algarve, Portugal; Coimbra, Portugal; Madeira Island, Portugal; Portalegre, Portugal; Bucharest, Romania; Slovakia; Catalonia, Spain; Leicestershire, UK; Northern Ireland, UK; Avellaneda, Argentina; Corrientes, Argentina; Paraguay; Lima, Peru; Caracas, Venezuela; Auckland, New Zealand.

Data points not labeled because of space constraints latitude in degrees, rate per , : Dalian, China 39, 1. Guilin, China 24, 0. Beijing, China 40, 0. Shanghai, China Chang Chun, China 44, 0. Jilin, China 43, 0. Shenyang, China 42, 0.

Lanzhou, China 36, 0. Nanning, China 23, 0. Zhengzhou, China 35, 0. Tie Ling, China 42, 0. Zunyi, China 28, 0. Wulumuqi, China 44, 0. Karachi, Pakistan 25, 0. Austria 48, 9. Hungary 47, 8. Turin, Italy 45, Lombardia, Italy 46, 7. Slovenia 46, 6. It was also reported that spring births were associated with increased likelihood of developing type 1 diabetes.

Sunburns - This is one of the most common side effects of too much sunlight. Symptoms of sunburn include redness, swelling, pain, tenderness or blisters on the skin. Eye damage - Too much exposure to UVB rays can damage the retina, which can increase the risk of cataracts. Ageing skin - Spending too much time in the sun can cause your skin to age faster.

Some people develop wrinkles and their skin becomes loose and leathery. Heatstroke - Heatstroke also called sunstroke is a condition in which the body's core temperature rises due to too much sun exposure.

Regular sun exposure is the most natural way to get enough vitamin D. But do not expose yourself too much and cover dark colour glasses to avoid eye damage. Note: Sun's UVB rays cannot penetrate through the window. So, people who sit next to sunny windows do not get vitamin D from the sun, contrary to what they believe.

Please Click Here to subscribe other newsletters that may interest you, and you'll always find stories you want to read in your inbox. A weekly guide to the biggest developments in health, medicine and wellbeing delivered to your inbox. Thank you for subscribing! Your subscription is confirmed for news related to biggest developments in health, medicine and wellbeing.

Back to Top. Select a City Close. Your current city: Mumbai Mumbai search close. All Bombay Times print stories are available on. We serve personalized stories based on the selected city OK. Go to TOI. The Times of India. Never say these things to a LEO.

Is number 13 really unlucky? Portugal makes it illegal for bosses to call employees after work. The death of a friend. These mental habits are turning you into a bitter person! How does your zodiac sign flirt? Is it good or hopeless? Find out now! Samantha Ruth Prabhu's revenge dressing game is on point. Chile's desert dumping ground for fast fashion leftovers.

Maharaja Padmanabh Singh of Jaipur is bringing back the moustache trend. Unisex hijab by rapper Ghali Amdouni is the hot thing in fashion world.